Is this a new sub-forum? Maybe I missed it before.
I agree that the Bosch "heavy" sections are superb. It's hard to describe it until you actually use these things, but the full-length T-slots allow for some amazing flexibility when it comes time to put things together, and they are far more rigid than one might think.
A few years ago, I finished a mill project using mostly Bosch elements, along with quite a bit of plate. While the extrusions are reasonably straight, for critical portions, like rail attachments, I think it is best to take a face mill to one side which creates a dead flat and true surface.
The solid steel T-nut sections are (by far) the best for attaching rails. Rather than 6 or 8 separate T-nuts, you have one individual long steel nut securing the rail, without any stress points created. But the "swivel-in-place" T-nuts are hard to beat for light-duty attachments and such.
The other beauty of these systems is that you can add attachments later in moments. For example, let's say you want to add a bracket for a mist cooling system. Normally you'd have to drill and tap a column, but with the t-slot sections, you make your bracket and on it goes using a swiveling t-nut. And you can reposition or remove it in moments.
The same applies to simple things like limit switches:
It's great stuff!